Cemented tungsten carbide materials is a group of very hard tool materials, often called hardmetals, which are obtained by liquid phase sintering tungsten monocarbide (WC) grains in a binder matrix which conventionally is cobalt or a cobalt rich alloy, although also other cementing or binding materials, such as iron, nickel, chromium, molybdenum and others may be employed. Normally, the content of matrix material amounts to about 3-8 wt-% of the total weight of the cemented carbide material but may be as low as about 1 or as high as up to about 20 wt-%. Recovery of tungsten from scrap from such cemented tungsten carbide tool materials is an important factor in the world's tungsten supply, but also the value of recovered cobalt should be recognized in this connection.
Today tungsten is mainly recovered from scrap cemented tungsten carbide powders by oxidization followed by chemical processing. From this source, other tradable tungsten raw materials can be produced, such as ferrotungsten. Ferrotungsten is mainly used when alloying with tungsten in steel production. It would be desirable if such tungsten carbide scrap could be recycled in a cost efficient manner to an intermediate tradable on the market.
A problem which may arise when alloying with ferrotungsten is that it may concentrate at the bottom of the melt where they may react with the furnace lining, which may affect the concentration of tungsten as well as the homogeneity of it in the melt.
WO2008091210 discloses an iron a tungsten containing powder comprising 30-60 wt % W and balance Iron. The powder is made by mixing an iron powder with a WO3-powder.